The present invention relates to a machine for applying adhesive to preset regions of products in general, particularly soles for shoes. In many industrial fields, and particularly in the field of shoes, there is the need to be able to apply to preset regions, i.e., at the upper edge of the sole in the case of shoes, a band of adhesive so as to bond the upper of the shoe.
The solutions of the prior art substantially provide for a machine in which the perimetric shape of the sole is acquired and then stored in a programmable processing unit, which drives a dispensing unit below which the sole is conveyed. During the application of the adhesive, the sole stationary and the dispensing unit is moved along two perpendicular directions on a plane, so that the dispensing nozzle can discharge, along a closed path, a jet of adhesive in a direction which is substantially perpendicular to the plane of arrangement of the sole.
This type of apparatus yields satisfactory results in the case of substantially flat soles which have no welt, but it is fully unsuitable in the case of contoured soles, soles with a welt and particularly so-called box soles, i.e., more generally, all soles with contours which form raised portions or have a peripheral region which lies on a plane other than the horizontal plane, so that acquiring the perimetric contour of the sole is not sufficient to allow easy application of the adhesive in the preselected regions. In the current situation, after the acquisition unit has acquired the images, it is necessary to perform considerable corrections in order to reconstruct an acceptable path for the movement of the nozzle, since the acquisition of the contour of the sole against a backlight can provide only partial information which is not sufficient to define a path in space.
Another drawback of the solutions of the prior art is the fact that since the adhesive has to be applied while the sole is stationary, the operating times are relatively long.